1. Scope of Invention
This invention relates generally to a tiltable truck bed of a dump truck, and more particularly to a tailgate apparatus for automatically pivotally opening and closing the tailgate apparatus of a dumpster box of a dump truck in an amount directly responsive to, and positively controlled by, the tilted angle of the truck bed.
2. Prior Art
A tailgate of a dump truck having a tiltable truck bed for emptying debris piled into the truck bed is typically attached to the upper rear ends of the side walls by a pivotal connection with the upper corners of the tailgate. When dumping a load of debris, the lower or bottom edge of the tailgate is released from a locked position by an operator and allowed to pivot outwardly from the side walls and the bottom of the truck bed as the truck bed is tilted upwardly.
To dump a load of debris, however, these typical dump trucks require that the operator physically unlock the tailgate before the truck bed is raised. Likewise, the operator must then resecure the otherwise freely pivotable tailgate before leaving the dump sight.
An improved tailgate apparatus is disclosed in U.S. Pat. No. 4,068,892 invented by Welch disclosing a tailgate apparatus which does apparently by gravity automatically raise and lower without the use of a power source and without the need for a locking device which prevents the tailgate from opening while debris is being transported within the truck bed.
However, all of the prior art devices and apparatus known to applicant, including the above Welch invention, do not provide for a positive means for lifting the tailgate above the plane of the upper margins of the side walls to readily facilitate dumping debris contained within the truck bed and which may be piled higher than the side walls. Typically, debris from tree cuttings, paper collection and other debris of a less dense nature can easily be piled above the side walls of the dump truck and remain there secured whether covered or uncovered, while being transported.
However, when the prior art dump truck bed is tilted for dumping, the debris piled high above the side walls will jamb and become wedged on the tailgate or tilting mechanism to prevent effective dumping. In such circumstances, the operator must again move to the rear of the truck bed and physically dislodge the jammed debris to effect complete dumping thereof.
An unpatented rear end dump truck is currently being manufactured by Workman and Sons, Inc. of Prineville, Oreg. which somewhat addresses this problem of dumping debris piled higher than the side walls of the truck bed. However, the Workmen-type and dump trucks address this issue by simply adding structure above the side walls near the ends thereof so that the pivotal point of the tailgate is substantially raised above the upper margins of the side walls.
Applicant is aware of several other patented prior art dump truck arrangements, none of which are as similar to the present invention as those prior art devices above described. These additional patented inventions are disclosed in the following U.S. patents:
U.S. Pat. No. 3,890,006 to Stockwell
U.S. Pat. No. 4,371,208 to Stricker
U.S. Pat. No. 4,699,428 to Vick
U.S. Pat. No. 4,059,307 to Neufeldt
U.S. Pat. No. 3,230,014 to Mufti, et al.
U.S. Pat. No. 4,343,511 to Rowan et al.
U.S. Pat. No. 4,659,147 to Smitneek
U.S. Pat. No. 5,030,053 to Wickizer
U.S. Pat. No. 5,100,279 to Bjerk
U.S. Pat. No. 4,269,039 to Baker
U.S. Pat. No. 1,363,917 to Read
U.S. Pat. No. 1,547,525 to Saxon et al.
U.S. Pat. No. 1,821,384 to Larson
U.S. Pat. No. 3,721,469 to Senesac et al.
U.S. Pat. No. 4,068,892 to Welch
U.S. Pat. No. 6,193,460 to Damico
In U.S. Patent 6,015,191, applicant does provide a tailgate apparatus for a dump truck which arcuately moves the tailgate in positive fashion in direct response to the angular tilting of the truck bed. The tailgate, when substantially fully opened by the truck bed being fully tilted for dumping, is positioned substantially above a plane defined by the upper margins of the side walls so that debris piled higher than the side walls will be easily dumped without the need for manual operator assistance. Further, the tailgate will be securely retained in the closed position without the need for operator locking, although same is preferred for secondary or supplemental insurance of tailgate lockage.
There has developed an unfilled need with respect to dumpster-type dump trucks which include a dumpster box which is removable from the truck bed. Typically, dumpster boxes are left at a refuse collection site such as a construction site, and then are removed after they are filled with debris. The present invention allows the dumpster box to not only be used in the conventional manner by being left at a collection site and then removed for refuge disposal by sliding the dumpster box on and off from a tiltable truck bed, but also adds the feature of a pivotal tailgate apparatus which will allow the dumpster box to function in the same fashion as the dump truck described in the previous ""191 referenced U.S. patent.
This invention is directed to a tailgate apparatus pivotally connected to a dump truck for automatically opening and closing a tailgate mounted at the rear of a dumpster box which, in the conventional mode of use, is supportively engaged atop and slidably or rollably removable from a tiltable truck bed of the dump truck. The tailgate is releasably secured against the ends of the side walls and bottom of the dumpster box when the truck bed is in a horizontal position. In a second mode of use, the truck bed is tiltable with respect to a chassis of the dump truck whereupon the tailgate arcuately opens in proportion to the angular tilting movement of the truck bed. The dumpster box may also be removed from the truck bed while maintaining the tailgate in a closed and secured condition.
It is therefore an object of this invention to provide a tailgate apparatus for a dump truck having a removable dumpster box which will automatically open in response to tilting of the truck bed of the dump truck, regardless of the character and volume of the load of debris in the dumpster box.
It is another object of this invention to provide a tailgate apparatus for a dumpster box-type dump truck which does not require the operator of the dump truck to release any locking mechanism of the tailgate prior to load dumping.
It is still another object of this invention to provide a tailgate apparatus for a removable dumpster box-type dump truck which will arcuately move from a closed position as the truck bed is tilted for dumping into a position substantially above the upper margins of the side walls to facilitate dumping of debris piled above the side walls in the dumpster box without the need for operator assistance.
It is yet another object of this invention to provide a tailgate apparatus for a dumpster box of a dump truck which will be held in a substantially closed position when the truck bed is in the horizontal position without the need for an operator locking the tailgate from random opening movement.
Still another object of this invention is to provide a tailgate apparatus for a dumpster box of a dump truck which allows for the dual modes of use of the dumpster box on both tilting and off-loading of the dumpster box and the tilt emptying thereof without removal of the dumpster box from the truck bed.